MODX Revolution 2.1.5-pl very slow

The problem occurs every few time in fact when I browse the site and delete the cache of Firefox is fast, however the site after an hour after the site is slow.
It seems like MODx has a cache that does this.
How can I fix the site is really slow. The problem is not the server. Hospita have other sites with MODx.

Does the same thing happen in Chrome or other browsers?

Have you considered upgrading to 2.2.0-pl2? It's much faster IMO. Even on local, which is always slower, it's faster.

I try with internet explorer,chrome,firefox and the effect in the same.
I considered upgrading to 2.2.0-pl2 but I'm afraid to mess it up

You can always re-install 2.1.5 if it does mess up. But it should be fine. Just make sure to set the default timezone in the manger to match what's set in php and mysql. Of course, php and mysql should also both match (and be set).

It really is loads faster. I can't believe how much faster it is on local. That's always been a problem for me.

you can give me a guide or suggestion to make the upgrade to 2.2.0-pl2 ?

Follow this:

http://rtfm.modx.com/display/revolution20/Upgrading+MODx

It's super smooth. Just upload the files, run setup, and let it upgrade.

I have this same problem. There is no better after upgrade. I have many other sites on modx 1.0.5 or Joomla with many images in content and in template - very fast. My site on Modx 2.2 is loading first time to 20s. There is 2 small images only. Firebug is showing: html - 20.18s , rest (css, js, images) - 0.31s, all 20.49. After moving site to my client sharing hosting speed is normal. Site is loading in 2.67s. 10 x faster !!!

I have dedicated server with php 5.3.9 , mysql 5 and apache 2.2. eAcceleator, zlib output compresion enabled. Instalation modx show everything on green. What modx 2 need else?

I try to install modx revo 2.2 but the problem is the same.
Read in the forums the problem is the Caching of Caching - MODx Revolution 2.x
In fact, when I save any document MODx clear the cache around the site causing a slowdown. There should be a cache control? If I edit a file should be removed from the cache only what?
This is what I found in the form. If it's really true that it is a tragedy.

I think that problem is in server configuration, not in Modx. My site on Modx 2.0 after moving to other server is fast. I was reinstall my server 1 month ago. I think that something is still missing for fast Modx. Its not modx's files or mysql cache. My site could loading and loading, but cache file is from 10-15 minuts ago. What Modx need for increase speed?

You might disable eAccelerator?